kubernetes/cmd/kubeadm/app/phases/upgrade/preflight.go

type CoreDNSCheck …

// Name is part of the preflight.Checker interface
func (c CoreDNSCheck) Name() string { … }

// Check is part of the preflight.Checker interface
func (c CoreDNSCheck) Check() (warnings, errors []error) { … }

// RunCoreDNSMigrationCheck initializes checks related to CoreDNS migration.
func RunCoreDNSMigrationCheck(client clientset.Interface, ignorePreflightErrors sets.Set[string]) error { … }

// checkUnsupportedPlugins checks if there are any plugins included in the current configuration
// that are unsupported for migration.
func checkUnsupportedPlugins(client clientset.Interface) error { … }

// checkMigration validates if migration of the current CoreDNS ConfigMap is possible.
func checkMigration(client clientset.Interface) error { … }